Abstract
Quasi-static anelastic experiments on YBa2Cu3Ox (x ≃ 6.45, T = 100 and 120 °C) demonstrate a relaxation process with a wide spectrum of activation enthalpies H for the relaxation times (⟨H⟩ ≃ 1 eV, σH = (0.07 ± 0.01) eV) and an extremely large relaxation strength Δ = 0.75 ± 0.15. The large Δ identifies the process as an oxygen redistribution between differently oriented sites in the CuO plane. The relaxation process characterizes the rate-determining step in long-range oxygen diffusion.